Adsorption of Dimers at Surfaces

Area of Science:

• Physical Chemistry
• Surface Science
• Statistical Mechanics

Background:

• Understanding molecular adsorption at surfaces is crucial for various chemical processes.
• Existing models often simplify molecular geometry, limiting applicability to complex molecules like dimers.
• The Ono-Kondo lattice theory provides a framework for studying adsorbed systems.

Purpose of the Study:

• To develop and present a generalized Ono-Kondo lattice model for dimer adsorption.
• To calculate the densities of parallel and perpendicular dimer orientations.
• To investigate the influence of dimer symmetry and interaction energy on adsorption behavior.

Main Methods:

• Generalization of the Ono-Kondo lattice theory for dimer adsorption.
• Calculation of site-averaged densities for parallel (x parallel) and perpendicular (x perpendicular) dimer orientations.
• Analysis of the model's predictions regarding preferential adsorption and Gibbs adsorption.

Main Results:

• The model predicts that symmetric dimer molecules preferentially adsorb parallel to the surface across all calculated densities.
• Calculations show distinct densities for parallel and perpendicular dimer orientations.
• The Gibbs adsorption is predicted to be negative when the interaction energy between dimers and the surface is small.

Conclusions:

• Symmetric dimers exhibit a strong preference for parallel adsorption on surfaces.
• The generalized Ono-Kondo model offers insights into the orientational behavior of adsorbed dimers.
• Surface interaction energies significantly influence the thermodynamics of dimer adsorption, potentially leading to negative Gibbs adsorption.